GaN substrates with variable vicinal angles for laser diode applications

GaN c-plane substrates were patterned to obtain 30-70 μm wide differently angled regions. The patterning technique was based on multilevel pattern photolithography and ion etching and was similar to the one used for the diffraction optics elements fabrication. The region angles were between 0.2 and 3.4 degrees with respect to the c-plane. It is shown that photoluminescence and cathodoluminescence wavelengths of InGaN/GaN quantum wells grown by metalorganic vapor phase epitaxy depend on each region's angle. Laser diodes grown on freestanding patterned GaN are also demonstrated. The lasing wavelength of chips grown in differently angled substrate regions are different. We attribute those differences to indium content differences in each of the angled regions.